When using the eclipse XML editor, using Alt+Shift+Up to 'Select
Enclosing Element' (and similar key bindings) don't seem to work.

Help --> Key Assist shows me the list of currently active key bindings
and I do see a listing as "Select Enclosing Element Alt+Shift+Up". I
also tried performing the same action through the menu Edit --> Expand
Selection To --> Selection Enclosing Element and it works fine.

It seems to me that the key binding is in place (and active) and the
action works (since I am able to use it through the Edit menu), but
looks like something else is missing? Is this a bug?